SYNTHESIS OF β-D-RIBONUCLEOSIDES DERIVED FROM DIPYRAZO[3,4-b:3',4'-d]PYRIDIN-3-ONE SYSTEM

The new ribonucleosides 8-methyl-2,6-diphenyl-5-(2,3,5-tri-0-benzoyl--D-ribofuranosyl)-2.//,6#dipyrazolo [3,4-b:3',4'-d]pyridin-3(5//)-one (la) and 8-methyl-2-(p-nitrophenyl)-6-phenyl-5-(2,3,5-tri-0-benzoyl-D-ribofuranosyl)-2//,6//-dipyrazolo [3,4-b:3',4'-d]pyridin-3(5//)-one (lb) were prepared from stannic chloride-catalyzed ribosylations of the corresponding heterocycles 6a and 6b. Attempts of de-O-benzoylation of la and lb failed to give the free ribosides lc and Id. The effect of compounds la, lb, 6a and 6b on the catalytic activities of reverse transcriptase from recombinant immunodeficiency virus type 1 was evaluated. Compounds lb and 6b inhibited the RNA dependent DNA polymerase activity of the enzyme by more than 50% at a concentration of 70 . In contrast, human placental DNA polymerase activities and were unaffected by this concentration. The structures of the nucleosides are supported by ID and 2D-nmr techniques (nOdes, HMBC and HMQC experiments).